I'm still trying to get the heater/defrost in my '92 4x4 automatic to work. The armrest heater works which as I understand is on a different system from the main heat. The 4Runner seems to be running at normal temp so I don't think it's the thermostat. I do see the two hoses going into the firewall just behind the motor, should I disconnect them and flush them out with a garden hose? I need some help, it's gettin really cold up here and the armrest heater doesn't put out enough heat for the whole truck.
Thanks.

http://personal.utulsa.edu/~nathan-buchanan/93fsm/airconditioning/25heater.pdf

Flushing the heater core is not a bad idea. Make sure the valve is opening allowing coolant to flow through the heater core. Make sure the flaps/dampers are opening allowing the flow of warm air.

Garden hose works IF you can get the connection together WITHOUT allowing air back in the system. Some parked on a steep incline to "burp" their heater system.
I found that, although a bit messy, is to let the engine run to where there is just a LITTLE pressure in the system, NOT FULL PRESSURE or HOT!!! Then crack the top heater hose open slightly a the the pipe and let the air out of the sliver of opening don't remove it completely as you need tomaintain the little presure and not let air back in. If you hear "gurgling" in your heater from inside the cabin then you still have air in you heater core. Like any good parent, keep burping until all the air has been released, then clean up the mess.:lol: